1. Field of the Invention
The present invention relates to a pumping apparatus that deforms cross-sectional shape of a tube made of an elastic material and discharges fluid filled therein.
2. Related Art
A pumping apparatus that discharges the fluid which is filled in a tube made of an elastic material (called “an elastic tube” hereinafter) wherein the cross-sectional shape of the elastic tube is deformed therein is well-known as a tube pump. The tube pump comprises a deforming mechanism that deforms the elastic tube in the surface vertical to the longitudinal direction thereof and inlet and outlet valves that occlude and de-occlude (called “relieve” hereinafter) the tube. The inlet valve occludes a portion of the elastic tube, the outlet valve relieves another portion of the tube and the deforming mechanism presses the part of the tube to deform the cross-sectional shape of the tube between these two portions so that the internal space of the tube shrinks to decreasing of cross-sectional area of the tube. The shrinkage of the inner volume of the tube enables to squeeze the fluid filled in the tube to transport it to the outlet valve along the longitudinal direction of the tube (squeezing period). After the squeezing (or transporting) is completed, the inlet valve relieves the occluded portion of the tube, the outlet valve occludes the relieved portion of the tube and the deforming mechanism returns to the position before the squeezing starts and then the fluid is filled into the internal space of the tube with the shape of tube returning to the initial shape posed by the elasticity of the elastic tube. Combining of the mechanical behaviors of tube pressing and returning by the deforming mechanism, tube occluding and relieving by the inlet valve and the outlet valve of a tube pump, it is possible to transport the fluid filled in the tube so that the tube pump, that is a kind of pumping apparatus, discharges the fluid filled in the tube.
Tube pumps are widely used to transport fluid such as liquid and gas in various application. Especially, it is very effective to transport the fluid from a container to another container via tube wherein the fluid needs to be uncontaminated by the external environment. The internal space of the tube, which is a passage of the fluid, being pressed to shrink, the fluid in the tube is transported without directly contacting with any other driving mechanism. Due to this advantage, tube pumps are used for medical infusion pumps that infuse medicine or solution to human bodies, fluid handling tools used for biological laboratories and orthochromatic control pumps to add toning agent to color ink.
Tube pumps can be roughly classified into a tube rotary pump and a peristaltic pumps. The former uses a roller as a tube deforming mechanism and inlet and out valves. Due to the simplicity of the mechanism, the former has been using old established technology and has a lot of varieties of discharge capacity (Reference 1 and 2). The latter uses a peristaltic mechanism as tube deforming mechanism. The mechanism is rather complicate, however the fatigue of tube is less and applicable to small capacity pumps. Among peristaltic pumps, a shuttle pump of which mechanism has a reciprocating motion part (shuttle part) is well-known (Reference 3 to 9).
FIGS. 38(a) to 38(c) show the principle of pump operation of a conventional pump. These figures show the pump operation described in Reference 4, wherein different numbers and codes from those used in Reference 4 are used.
A shuttle pump 1000 fundamentally comprises a tube 1001, a shuttle mechanism 1002 as a deforming mechanism, an inlet valve mechanism 1003 as an inlet valve and an outlet valve mechanism 1004 as an outlet valve. In the shuttle mechanism 1002, the inlet valve mechanism 1003 and the outlet valve mechanism 1004 synchronously operate. They periodically deform and undeform (or relieve the deformation of) the tube 1001 and transfers the fluid filled in the tube 1001 from the upper stream to the downstream. The region of the tube 1001, which is between the inlet valve mechanism 1003 and the outlet valve mechanism 1004 makes pump operation such as filling and discharging the fluid that flows the tube 1001. This region is called “pump region” hereinafter.
In order to fill the fluid in the pump region of the tube 1001, the inlet valve mechanism 1003 relieves the inlet side of the tube 1001, the outlet valve mechanism 1004 occludes the outlet side of the tube 1001 and the shuttle mechanism 1002 relieves the deformation of the tube 1001, as shown in FIG. 38(a). By these motions of mechanism, the fluid is filled in the pump region of the tube 1001.
Subsequently, the outlet side of the tube 1001 is, as shown in FIG. 38(b), relieved by the outlet valve mechanism 1004 and the inlet side of the tube 1001 is occluded by the inlet valve mechanism 1003 under the status that the pump region of the tube 1001 in which the fluid is filled. With shrinking of the internal space of the tube 1001 by the shuttle mechanism 1002 that deforms the tube 1001 as shown in FIG. 38(c), the fluid filled in the pump region of the tube 1001 is transported to the downstream through the outlet side of the tube 1001 which is relieved by the outlet valve mechanism 1004.
Then, as shown in FIG. 38(a), the inlet valve mechanism 1003 relieves the inlet side of the tube 1001, the outlet valve mechanism 1004 occludes the outlet side of the tube 1001 and the shuttle mechanism 1002 undeforms (or relieves the deformation of) the tube 1001. In order to fill the fluid in the pump region of the tube 1001. By this set of motions, the shape of the tube 1001 return to the initial shape and the internal space of the tube 1001 at the pump region increases from that of the shrunk tube shape to that of intrinsic initial tube shape. The incremental volume of the internal space is filled with the fluid supplied from the upper stream of the fluid.
The motion of the inlet valve mechanism 1003 and the outlet valve mechanism 1004 being in synchronous to that of the shuttle mechanism 1002, the fluid filled in the tube 1001 is transported from the upper stream to the downstream by repeating the deformation and undeformation (or relieving the deformation) of the tube 1001 by the shuttle mechanism.
FIG. 39 shows the cross-sectional view of an example of shuttle mechanism adopted in a prior art (Reference 4).
The shuttle mechanism of this example uses a specially-shaped tube 1011 and comprises jaw members 1012 and 1013 which are set in left and right sides of the specially-shaped tube 1011. The jaw members 1012 and 1013 ridge parts 1014 of the specially-shaped tube 1011 are composed at the upper part and the lower part and these parts face against to tuck the specially-shaped tube 1011 therebetween. The direction of tucking which is upper/lower direction in the FIG. 39 is called Y direction.
The jaw members 1012 and 1013 synchronously move in the same direction. The upper part and the low part of the jaw members 1012 and 1013 move mutually in the reverse orientation in Y direction so that both jaw members 1012 and 1013 press the specially-shaped tube 1011 resulting in the inner volume of the specially-shaped tube 1011 in which the fluid is filled to shrink. Valve mechanisms are set in the upper stream line and the downstream of this shuttle mechanism. The fluid filled in the internal space of the specially-shaped tube 1011 does not reversely flow due to the intervention of valve mechanism set in the upper stream and downstream. On the other hand, the fluid filled in the internal space of the specially-shaped tube 1011 is pressed toward the downstream part of the specially-shaped tube 1011 without the intervention of the valve mechanism set in the downstream. The behavior of fluid being pressed turns into the transportation of the fluid filled in the internal space of the specially-shaped tube 1011. The upper and lower parts of the jaw members 1012 and 1013 move in Y direction to de-press (or relieve from pressing) the specially-shaped tube 1011, the specially-shaped tube 1011 returns to the initial shape due to the elasticity and then the internal shape recovers to have the initial volume. In synchronous to this motion, the upper valve mechanism relieves the specially-shaped tube 1011 and the lower valve occludes the specially-shaped tube 1011. Then the fluid is supplied from the upper stream when the specially-shaped tube 1011 returns to the initial shape. By repeating these motions, the flow is transported only towards downstream and overall pumping motion is generated.
FIG. 40 shows the cross-sectional view of a shuttle mechanism of another example of prior arts. This shuttle mechanism is described in Reference 3.
The shuttle mechanism used for this example of prior art comprises two members that deform the tube 1020 of the tube pump. The members 1021 and 1022 mutually move in parallel. The members 1021 and 1022 do not deform the tube 1020 so that the cross-sectional shape is kept as its initial one at one end of the parallel motion as it is, but press the tube 1020 so that the cross-sectional shape is deformed and the internal space of the tube 1020 in which the fluid is filled shrinks at the other end of the parallel motion as shown in FIG. 40. The shrinkage of the internal space of the tube 1020 results into discharging of the fluid filled in the tube 1020 toward the downstream.
The shuttle mechanism as shown in FIG. 39 needs the specially-shaped tube 1011 that requires a ridge line so that the specially-shaped tube 1011 does not digress from the jaw members 1012 and 1013. Therefore a conventional tube that is a hollow tube with round cross-sectional shape is not used for this tube pump. On the other hand, the shuttle mechanism as shown in FIG. 40 needs additional mechanism such that the tube 1020 is set to and unset from the members 1021 and 1022. For this set and unset motion, one of the members 1021 and 1022 should be rotated at an axis in the end part thereof so that an open inlet or outlet space is made and the tube 1020 can slide in the horizontal direction to be set in or unset from the members 1021 and 1022. To realize such motion, a complicated mechanism has to be additionally installed in the shuttle mechanism for the actual pump mechanism.
FIGS. 41(a) and 41(b) further shows another example of a prior art of the shuttle mechanism. This shuttle mechanism does not need a specially-shaped tube therefore allows to easily set and unset the tube. There it can be said that this shuttle mechanism have a practical implementation as a tube pump.
The shuttle mechanism shown in FIGS. 41(a) and 41(b) comprise two shuttle members 1031 and 1032 which hold the tube 1030 therebetween and extend along the tube (vertical to the page) in a planar shape. According to the shape of the shuttle viewed from the back side of the tube holding surface, a name “shuttle plate” is used instead of “shuttle member”. The shuttle members 1031 and 1032 have grooves 1033 and 1034, respectively. These grooves 1033 and 1034 form a space that stores the tube 1030 without deforming the cross section of the against the tube 1030 when they completely face to the other.
The shuttle members 1031 and 1032 can slide against each other with a gap that keeps certain distance each other in the direction vertical to the direction of sliding thereof (that is, sliding direction) as shown in FIG. 41(a). When the shuttle member 1032 slides against the shuttle 1031, the groove 1034 does against the shuttle 1033 and the tube 1030 turns to be pressed to deform. Then the cross section of the tube 1030 deforms and the internal space of the tube 1030 shrinks to decrease so that the fluid filled in the internal space is discharged to the downstream of the tube 1030 with the motion of the valves synchronous to the shuttle members 1031 and 1032.
In the shuttle mechanism shown in FIGS. 41(a) and 41(b), the tube 1030 is held in the grooves 1033 and 1034 made in the shuttle members 1031 and 1032. The tube setting and holding process (in other words, mounting process) is that the tube 1030 is put into the groove 1033 or 1034 after expanding the gap between the shuttle members 1031 and 1032 and then the gap is narrowed to return the initial gap between the shuttle members 1031 and 1032. Since the grooves 1033 and 1034 are simple shapes, the mounting and dismounting of the tube 1030 into and from the shuttle mechanism can be easily realized and such mechanism for tube mounting and dismounting can be implemented with simple part assembly. Due to this features, this shuttle mechanism is applied to actual volumetric infusion pumps.
Whichever the shuttle mechanisms are, deviation of flow rate in liquid transportation is strongly required to be little. For example, the shuttle mechanism shown in FIGS. 41(a) and 41(b) works as the shuttle member 1032 horizontally slides along the surface of the shuttle member 1031 in parallel with the keeping consistent gap therebetween and the tube 1030 is pressed to deform as shown in FIG. 41(b). This deformation depends on the physical shapes of the grooves 1033 and 1034 and sliding width but not the material of the tube 1030 in principle.
For the other peristaltic pumps, a plurality of mechanical elements that press to deform a tube is adopted to construct the pump mechanism that presses the tube at a plurality of pressing points or portions. Therefore the internal spaces of the tube are determined by the balance between the pressing force by the pump mechanism and the resilience force of the tube. In other words, one tube region that is pressed to deform by the mechanical elements and the other tube region that returns to the initial shape due to resilience alternatively present along the tube. Therefore the volumes of the internal spaces of the tube region vary or deviate by the force balance between pressing and resilience. As the results, the flow rate of the liquid discharged from the pump varies or deviates due to the variation or deviation of the tube materials and the elasticity that depends on the ambient temperature. From these reasons, sufficient precision and stability of the flow rate are hardly obtained.
Example of the conventional peristaltic pumps and shuttle pumps are found in, for example, the following patent documents, all of which are incorporated by reference:    [Patent Document 1] Japanese Patent Application Publication No. 2003-113782    [Patent Document 2] Japanese Patent Application Publication No. 2003-254260    [Patent Document 3] U.S. Pat. No. 4,936,760    [Patent Document 4] U.S. Pat. No. 5,151,019    [Patent Document 5] U.S. Patent Application Publication 2007/0048161    [Patent Document 6] Japanese Unexamined Patent Application Publication No. 11-0508017    [Patent Document 7] Japanese Patent Application Publication No. 2003-049779    [Patent Document 8] Japanese Patent Application Publication No. 2003-286959    [Patent Document 8] Japanese Patent 4511388